User's Manual

transceivers that are dispersed throughout a region. Yagi antennas are most effective at fixed remote sites in a
master/slave network that simply need to exchange packets directly with a single node in the network.
The coaxial cable assemblies that accompany each of the NovaRoam™ 900 antennas are designed to be mated to
the antenna and the NovaRoam™ 900 antenna port. There is only one way to make this connection since the
antenna uses a Type N connector while the NovaRoam™ 900 employs an RP-TNC. The coupling nuts should
only be hand tightened. Pliers or wrenches should not be used since they might generate excessive torque,
damaging the connector interface. Once the coax has been attached to the antenna, apply a layer of Vapor-
Wrap™ around the joint at the antenna to prevent moisture in the outdoor environment from corroding this
connection. This is accomplished by removing the paper backing from the Vapor-Wrap™ and laying it against
the connector pair so that the connectors are in the center of the patch. Wrap the Vapor-Wrap™ around the
connectors and cables, pushing and working the compound into all cracks. Smooth the compound onto the
cable jacket. When complete, the joint should have a smooth, tapered appearance.
The antenna should be located so that there is a clear line of sight to every other NovaRoam™ 900 transceiver
that it intends to communicate with directly. Obstacles such as buildings and foliage generally reduce the
resulting received signal strength and thereby degrade link performance. In the case of omni and Yagi antennas,
a clear line of sight can often be achieved by mounting the antenna on a mast to obtain clearance over
obstructions. The NovaRoam™ 900 must be mounted within an enclosure to shield it from rain and condensing
humidity, reducing its exposure to the elements. Finally, remember to point the Yagi antenna in the direction of
its destination. In certain situations, minor changes in the pointing and height of the antenna can yield
noticeable improvements in link margin. Therefore be prepared to make some adjustments from the initial
settings if this advantage is needed. This is best achieved by performing NovaRoam™ 900 link tests at several
different orientations, and noting the position that delivers the best results.
CAUTION
The NovaRoam™ 900 has been specifically designed to close the longest possible links. This goal has been
accomplished in part by delivering the highest permissible RF output power to the antenna per the FCC Part 15
Rules. In August 1996, the FCC adopted RF exposure guidelines that established safety levels for various
categories of wireless transceivers. Those limits are consistent with safety standards previously published by
the National Council on Radiation Protection (NCRP) Report 86, §17.4.1, §17.4.1.1, §17.4.2, and §17.4.3 as well as
the American National Standards Institute (ANSI) in §4.1 of “IEEE Standard for Safety Levels with Respect to
Human Exposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz,” ANSI/IEEE C95.1-1992. The
NovaRoam™ 900 user can comply with this FCC guideline by maintaining a minimum separation from any
NovaRoam™ 900 antenna of at least 9” (22.8cm). As a consequence, the user should disconnect the AC/DC
input power source from the NovaRoam™ 900 whenever repositioning the antenna.
DSSS signals, by their very nature, produce wideband spectra in order to mitigate the effects of interference. As
a consequence, these signals will tend to intermingle when multiple channels are deployed in overlapping
physical regions. Nova Engineering has devised a remedy to this challenge by allowing these networks to select
“sync sets” consisting of specially constructed PN sequences and frame synchronization preambles. These
words have been selected to have minimum cross correlation and thereby serve as passwords to limit access to a
network. A user operating within Network A cannot access channels on Network B since their passwords do
not match. The NovaRoam™ 900 includes four sync sets for each of its seven operating modes. There are
limitations to this strategy since even though access can be effectively denied in this way, it does not prevent
interference between the competing signals. As a result, it is always best to strive to obtain the widest possible
frequency separation between channels in overlapping networks.